1. Field of the Invention
This invention relates to electronic control apparatus and in particular, but not exclusively, to an electronic throttle box for controlling an engine of an aircraft. The invention does however extend more widely to any electronic control apparatus in which a moveable control member exerts a control function either directly or indirectly.
2. Discussion of Prior Art
In an aircraft, the throttle box is a sophisticated item of equipment, allowing the pilot manually to control the aircraft thrust whilst giving him tactile feedback to indicate various conditions or operating regimes of the engine. In addition the throttle box should be designed so that the control member or "throttle top" is not moved inadvertently by vibration or acceleration experienced by the aircraft in use.
Thus the requirements imposed on a throttle box for it to be suitable for use in a modern fighter aircraft result in extremely complex mechanical designs which are expensive and difficult to produce, requiring as they do the services of skilled and highly trained personnel for their assembly and set up; for example the throttle box for use on a typical modern fighter aircraft might easily require a development outlay of around fifty thousand man hours. This complexity derives primarily from the requirement for tactile feedback implement base friction throughout the travel of the throttle top and mechanical detents to provide demarcation between distinct areas of operation such as dry and re-heat, whilst contending with the rigours of a cockpit environment--notably vibration.